Changed default gerrit checkout branch, fixed gating

Change-Id: I1274b72e6d49460ab4317e1305d523834a758cf8
diff --git a/test-salt-models-pipeline.groovy b/test-salt-models-pipeline.groovy
index 1a31f88..05695b2 100644
--- a/test-salt-models-pipeline.groovy
+++ b/test-salt-models-pipeline.groovy
@@ -37,7 +37,7 @@
           credentialsId : CREDENTIALS_ID
         ])
       } else if(defaultGitRef && defaultGitUrl) {
-          checkouted = gerrit.gerritPatchsetCheckout(defaultGitUrl, defaultGitRef, "master", CREDENTIALS_ID)
+          checkouted = gerrit.gerritPatchsetCheckout(defaultGitUrl, defaultGitRef, "HEAD", CREDENTIALS_ID)
       }
       if(checkouted){
         if (fileExists('classes/system')) {